Telecommunications networks are commonplace today and typically operate in accordance with a given standard or specification. These standards ensure interoperability between telecommunications devices and are defined by organisations such as the, Internet Engineering Task Force (IETF), Wireless Ethernet Compatibility Alliance (WECA), and the International Telecommunication Union (ITU).
As with wired networks, wireless networks can be classified into different types based on the coverage area. These include wireless wide area networks (WWAN), wireless metropolitan area networks (WMANs) and wireless local area networks (WLANs).
WLAN technologies enable users to establish wireless connections within a local area, for example, within a user's house, a corporate building or in a public space, such as an airport. In 1997, the IEEE approved the 802.11 standard for WLANs. The IEEE802.11 standard is commonly referred to as Wi-Fi and has been rapidly deployed across the globe since its inception as an alternative to traditional wired network solutions. The introduction of Wi-Fi has revolutionised wireless networking and has been further developed with the introduction of Wireless Mesh Network (WMN).
A typical WMN consists of multiple nodes connected in a mesh topology. The nodes can be wireless routers, also known as access points (APs), or wireless clients. In a mesh topology, the nodes in the network have redundant or multiple communication paths with its destination node. The routers usually have limited mobility and form the infrastructure or backbone of the WMN. In contrast, the clients are not usually limited to being stationary. Both the clients and the routers can organise and configure themselves autonomously to interconnect wirelessly to form the mesh structure, often creating redundant communication paths, which is an inherent characteristic of the mesh topology. The mesh topology makes the WMN particularly resilient and robust towards interference, failing nodes and congestion, as well as being highly scalable due to its ability to autonomously configure and organise connecting nodes. The radio technology widely employed in most WiFi networks, such as WMN, utilises a single radio.
Mesh networks are highly scalable, hence adding nodes to a particular network is easy as the physical location of the node that is being added is immaterial. The node can be placed anywhere within the network's communication range, and it will automatically configure itself and connect to the nearest node in order to communicate with its destination node. While the location of the node is immaterial, the node might have to utilise several hops in order to communicate with its destination. The number of hops taken is dependent on the location of the node and the corresponding location of the destination node.
The medium access control (MAC) layer/algorithm normally determines how network capacity is allocated to clients. In a conventional Wi-Fi router, the MAC layer will control the admission of a particular set of clients and control allocation of bandwidth among all clients connected to the router. Presently, a router allocates a predetermined amount of bandwidth to each client, which is determined by the total capacity of the network. However, problems arise in wireless mesh networks where there are multiple interconnected routers, each with separate clients attached to them. The situation is described below with reference to FIG. 1.
FIG. 1 illustrates a wireless network 100 in a multihop scenario. The network 100 comprises a bandwidth source or sink 102, a gateway 104, and router 106. The gateway 104 is connected to the sink 102 and the router 106. The gateway 104 is also connected to a client (client1) 108. The router 106 is connected to two clients, client2 110 and client3 112.
In known arrangements, both the gateway 104 and the router 106 are allocated the same bandwidth. Whilst this may appear to be fair, gateway 104, and indeed any other router, treats all nodes connected equally as clients. Therefore, gateway 104 treats the router 106 as another client and only allocates the connection between the gateway 104 and the router 106 the same bandwidth as the connection between the gateway 104 and client1 108. Thus, router 106 only has the same bandwidth allocation as client1 108, and has to share this allocated bandwidth with its two clients, client and client. The result is that bandwidth in the network is biased in favour of those nodes that are nearest, in the sense that they are the separated by the fewest hops, to the gateway or bandwidth source. The problem is therefore to provide a fair allocation of bandwidth across all nodes in a wireless network, irrespective of their physical location in the network.
This problem is regularly observed in multihop scenarios such as the one described above. However, as multihop scenarios are ubiquitous in WMN, the same problem also exists in WMNs.
Most current routing implementations in WMNs utilise ad-hoc routing protocols, such as ad-hoc on demand distance vector routing (AODV) and dynamic source routing (DSR), based on the notion that ad-hoc networks are very similar to WMNs. However, this ignores the fact that a WMN consists of mesh routers, which act as relaying nodes and APs. The requirements of the mesh routers are different as compared to the requirements of the mesh clients. Clients in ad-hoc networks are similar to the mesh clients but not to the mesh routers. Therefore, conventional ad-hoc routing protocols cannot efficiently provide a framework for fair distribution of bandwidth in a WMN. Furthermore, the MAC extension provided by 802.11e for QoS does not cater for this problem.
In “Providing Throughput Guarantees in IEEE 802.11e Wireless LANs” by Albert Banchs et al., Proceedings of the 18th International Teletraffic Congress (ITC-18), Berlin, Germany, Sep. 1-05, 2003, there is described a method for improving the throughput (bandwidth) guarantees in the 802.11e EDCF mechanism based on deducing new contention window sizes. The method enables an access point to provide throughput guarantees and admit as many clients as possible based on those guarantees. However, the method is only concerned with bandwidth aggregation between an access point and its clients and does not consider bandwidth aggregation between access points. Furthermore, the method described does not allocate bandwidth fairly and evenly between all clients. Instead it merely allows a single router to maximise the number of clients it can have connected and provides some throughput guarantees.